Carbon monoxide binding properties of domain-swapped dimeric myoglobin
Carbon monoxide binding properties of domain-swapped dimeric myoglobin
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结构域交换二聚肌红蛋白的一氧化碳结合特性
DOI：
10.1007/s00775-014-1236-0
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发表时间：
2015
影响因子：
3
通讯作者：
Shun Hirota
中科院分区：
文献类型：
--
作者：
Satoshi Nagao;Haruto Ishikawa;Takuya Yamada;Yasuhisa Mizutani;Shun Hirota
肌红蛋白（Mb）是一种单体储氧血红素蛋白，并已被证明形成结构域交换的二聚体。在这项研究中，单体和二聚一氧化碳（CO）结合Mb（MbCO）表现出相似的吸收光谱。对于单体和二聚体MbCO，在1，932和1，944 cm− 1处观察到MbCO的CO伸缩频率。对于脱氧Mb（deoxyMb）和MbCO的单体和二聚体，分别在相同的频率下观察到血红素铁和轴向配体之间伸缩的共振拉曼（RR）带（νFe-His，220 cm−1;νFe-C，507 cm−1），表明脱氧Mb的Fe-His键强度和MbCO的Fe-CO键强度没有因二聚化而改变。时间分辨的RR测量表明，血红素活性位点的结构变化的动力学在单体和二聚体Mb之间是相似的[单体，（5.2 ± 1.8）× 106 s −1;二聚体，（6.2 ± 1.1）× 106 s − 1在室温下]。这些结果表明，血红素的配位结构，周围的结合CO的蛋白质环境，和蛋白质松弛特性之间的单体和二聚体MbCO是相似的。尽管Mb的活性中心结构与二聚体相似，但二聚体Mb的CO结合速率常数[（1.01 ± 0.03）× 106 M-1 s-1（20 °C）]大约是单体[（0.52 ± 0.02）× 106 M-1 s-1（20 °C）]的两倍，推测是由于二聚作用导致Xe 3腔和溶剂之间的通道膨胀。
Myoglobin (Mb) is a monomeric oxygen storage hemoprotein, and has been shown to form a domain-swapped dimer. In this study, monomeric and dimeric carbon monoxide (CO)-bound Mb (MbCO) exhibited similar absorption spectra. The CO stretching frequencies of MbCO were observed at 1,932 and 1,944 cm−1for both monomeric and dimeric MbCO. The resonance Raman (RR) bands for the stretching between the heme iron and axial ligands were observed at the same frequencies for the monomer and dimer of deoxygenated Mb (deoxyMb) and MbCO, respectively (νFe–His, 220 cm−1;νFe–C, 507 cm−1), showing that the Fe–His bond strength of deoxyMb and the Fe–CO bond strength of MbCO did not change by the dimerization. Time-resolved RR measurements showed that the dynamics of the structural changes at the heme active site after CO photo-dissociation of MbCO was similar between monomeric and dimeric Mb [monomer, (5.2 ± 1.8) × 106s−1; dimer, (6.2 ± 1.1) × 106s−1at room temperature]. These results show that the heme coordination structure, the protein environment around the bound CO, and the protein relaxation character are similar between monomeric and dimeric MbCO. Although the active site structure was similar between the monomer and dimer, the CO binding rate constant of dimeric Mb [(1.01 ± 0.03) × 106M−1s−1at 20 °C] was about twice larger than that of the monomer [(0.52 ± 0.02) × 106M−1s−1at 20 °C], presumably due to the expansion of the channel between the Xe3 cavity and the solvent by the dimerization.